1. Field of the Invention
The present invention relates to a coupling clamp, and more particularly to an inner shield coupling clamp which does not damage and peel a blackened layer formed on an inner shield.
2. Description of Related Art
Generally, in a cathode-ray tube of a television and a display, especially, in the cathode-ray tube of a shadow mask type, a frame is arranged inside a face panel to support a shadow mask. In addition to the shadow mask, an inner shield is installed in this frame to reduce influence of earth magnetism. A blackened layer is formed on the inner shield. The frame and the inner shield are coupled by an inner shield coupling clamp. When the frame and the inner shield are attached, the inner shield coupling clamp is required to be easily inserted in a common hole passing through the frame and the inner shield. Also, the inner shield coupling clamp is required to have the strong strength to hold them in a tightly coupled state.
FIG. 1 is a general perspective view to explain a coupling state of the frame and the inner shield. As shown in FIG. 1, the inner shield S is put on the frame F and the inner shield coupling clamp 11 which has the above-mentioned elastic structure is inserted in common through-holes H. Thereby, the frame F and the inner shield S are coupled as a unitary body.
FIG. 2 is a perspective view of the first conventional example of inner shield coupling clamp. As sown in FIG. 2, a band-shape elastic metal body is bent in a V-like shape at the center portion in the longitudinal direction of the elastic metal body to form a center bending portion 12. The first bending portions 13, the second bending portions 14, the third bending portions 16 are sequentially formed in a line symmetrical manner with respect to the center bending portion 12 as a convex portion. As a result, the inner shield coupling clamp 11 is formed to have an elastic structure. The fourth extending portions 17 from the third bending portions 16 to tip portions of the elastic metal band is a picking-up section and a holding section is composed of the second extending portions between the first bending portions and the second bending portions and the tip portions of the fourth extending portions to hold the frame and the inner shield in the coupled state. The inner shield coupling clamp holds the frame F and the inner shield S by the holding section 15 of the inner shield coupling clamp 11.
There is a case where the tip portion 17a of the fourth extending portion 17 has a metallic broken-out section and the blackened layer formed on the inner shield S is sometime damaged and peeled. In this case, mask holes of the shadow mask is filled with the blackened layer peeled off from the inner shield and the breakdown voltage characteristic of the electron gun structure is degraded. As a result, the peeled blackened layer sometimes has a bad influence to the characteristics of the cathode-ray tube.
The work to insert the inner shield coupling clamp 11 into the through-hole is hand-worked. However, because the picking-up portion 17 of the first conventional example of the inner shield coupling clamp 11 is small, the inner shield coupling clamp 11 cannot be easily picked up by a hand. Also, the workability is not good to drop the inner shield coupling clamp 11 on the way of coupling the frame and the inner shield.
FIG. 3 is a cross sectional view illustrating the clamping state in which the frame and the inner shield are clamped by the second conventional example of the inner shield coupling clamp. The inner shield coupling clamp shown in FIG. 3 is disclosed in Japanese Laid Open Patent Disclosure (JP-A-Heisei 4-233134). In the inner shield coupling clamp, the tip portions of the holding section is bent in an outside direction to have an obtuse angle equal to or more than 90 degrees. The inner shield is pushed to the frame by the tip portions. In the structure, the tip portions have a metallic broken-out section like the above-mentioned example, the blackened layer of the inner shield 31 is damaged and sometimes peeled.
On the other hand, FIG. 4 is a cross sectional view illustrating the clamping state in which the frame and the inner shield are clamped by the third conventional example of the inner shield coupling clamp. The inner shield coupling clamp shown in FIG. 4 is disclosed in Japanese Examined Patent Disclosure (JP-B2-Showa 62-13787). In the inner shield coupling clamp, the inner shield 41 is pushed to the frame by the shoulder portions 40a. Because the inner shield 41 is pushed by the shoulder portions 40a, a blackened layer on the inner shield 41 is rarely injured and peeled. However, the third conventional example of the inner shield coupling clamp has the structure In which it is difficult to pick up the coupling clamp. Therefore, the structure should be improved on the workability.